We now have silk fabric that glows under black lights created in three different ways. First, you can buy silk that has been dyed with fluorescent dye. Or you can use silk that was spun by silkworms that have been fed fluorescent dye. But now we also have silk that has been spun by silkworms that have been genetically modified with genes from fluorescent protein-producing animals. In three different colors!

Creating the glowing silks meant borrowing from organisms that already produce fluorescent molecules. Scientists inserted the DNA sequences that produce these foreign fluorescent proteins into the silkworm genome, creating what’s called a transgenic animal. One batch got a red, glowing protein normally found in Discosoma corals; another got a glowing orange protein from the Fungia concinna coral. The third strain incorporated the green fluorescent protein derived from jellyfish.

When the silkworms started spinning, the glowing sequences turned on and produced silk in three different colors — and the colors stayed vibrant and glowing for more than two years. Scientists bred and reared more than 20,000 of these transgenic silkworms in the lab, feeding them mulberry leaves, harvesting their shimmering threads and working out how to turn the raw, glowing cocoon silk into a functional material. Because the processing steps for normal silk — such as cooking cocoons at 100 degrees Celsius — destroy fluorescent proteins, the scientists needed to find a slightly different way to produce the fabrics. In the end, they found that a combination of slightly lower temperatures, an alkaline solution, and a vacuum produced softened cocoons that could be reeled.